Safety devices for gas welding, cutting and allied processes

This paper describes the results of extensive research to determine the limit of safety against flame transmission for sintered metal flame arrester elements when stressed by a flashback in a fuel-gas/oxygen mixture and when stressed through a stabilized burning of a flowing mixture of fuel-gas and air and of fuel-gas and oxygen at the sintered metal element. On the basis of the results of these investigations, the limit of safety against flame transmission for sintered metal flame arrester elements can be estimated and the conditions for testing can be specified. An analysis of the protection of gas outlets on gas distribution lines for welding, cutting and allied processes has been carried out, resulting in recommendations for necessary changes to the regulations for testing of safety devices with sintered metal flame arrester elements, which should be made in the next revision of the corresponding technical regulations for acetylene installations and calcium carbide stores (TRAC), and the standards DIN 8521, EN 730 and ISO 5175.     

Diamondback terrapins as indicator species of persistent organic pollutants: Using Barnegat Bay, New Jersey as a case study

The diamondback terrapin’s (Malaclemys terrapin) wide geographic distribution, long life span, occurrence in a variety of habitats within the saltmarsh ecosystem, predatory foraging behavior, and high site fidelity make it a useful indicator species for contaminant monitoring in estuarine ecosystems. In this study fat biopsies and plasma samples were collected from males and females from two sites within Barnegat Bay, New Jersey, as well as tissues from a gravid female and blue mussels (Mytilus edulis), which are terrapin prey. Samples were analyzed for persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), chlorinated pesticides, and methyl-triclosan. Terrapins from the northern site, Spizzle Creek, closest to influences from industrial areas, had higher POP concentrations for both tissues than terrapins from the less impacted Forsythe National Wildlife Refuge. Sex differences were observed with males having higher contaminant concentrations in fat and females in plasma. PCB patterns in terrapin fat and plasma were comparable to other wildlife. An atypical PBDE pattern was observed, dominated by PBDEs 153 and 100 instead of PBDEs 47 and 99, which has been documented in only a few other turtle species. The typical PBDE patterns measured in mussels, terrapin prey, suggests that the terrapin may efficiently biotransform or eliminate PBDE 47 and possibly PBDE 99. Plasma contaminant concentrations significantly and positively correlated with those in fat. This study addresses several aspects of using the terrapin as an indicator species for POP monitoring: site and sex differences, tissue sampling choices, maternal transfer, and biomagnification.     

Dr Gwyneth Dorothy Howells (1925–2009), former Editor in Chief of Chemistry and Ecology

This paper presents the results of the examination of concentrations of chlorinated hydrocarbons in surface sediments from the middle of the Adriatic. the sampling area was chosen as part of the protection programme of the Adriatic Sea and is located at two transverse transects, each consisting of four stations. the sediments were collected during the summer cruise of 1990. Quantification of individual components was performed by Capillary Gas Chromatography (CGC) using reference standards. Areal distribution of the concentrations of HCB, lindane, DDT and its metabolites, dieldrin, endrin and PCBs are presented. the values obtained varied within a wide range of concentration from 20 pg/g dry weight for lindane to 700 pg/g dry weight for Σ DDT and the sum of PCBs as Aroclor 1254 from 0.3 to 6.6 ng/g.

The main source of these compounds is thought to be from suspended matter entering the Adriatic sea via the River Po and transported by currents to its middle part.     

Particle image velocimetry (PIV) analysis of flame structure

An experimental study of methane–air flame propagation in a duct is reported. A flat duct was chosen to allow optical visualization and flame propagation measurements. The duct was equipped with optical-quality windows to allow Schlieren visualization and particle image velocimetry (PIV) velocity measurements. The flame propagation velocity, flow structure, and velocity distribution in the flame for a different air excess factor are reported.     

Experiments and numerical simulation on methane flame quenching by water mist

The study of extinguishment using water mist has been motivated due to the phase-out of the use of halens and the search for alternative means that preserve all of the benefits of a clean total flooding agent without adverse environmental impact. With the numerical simulation, we analyzed a gas–liquid two-phase problem including water (liquid), air and methane (gas) using Eulerian equations for the liquid phase and the full Navier–Stokes equations for the gas phase. Gaseous mass, momentum and energy equations are integrated simultaneously by a Harten–Yee explicit non-MUSCL modified-flux type TVD scheme for the convective terms and a central difference scheme for the viscous terms. Liquid phase conservation equations are solved with an application of a flux-vector-splitting scheme. In the experiments in an open room (500×500×500 mm) we observed an interaction of the diffusion flame with the water mists. The results show remarkable flame quenching and a good agreement between the numerical and experimental results.     

气体爆轰波在弯曲管道中传播特性的实验研究

对丙烷 -空气爆轰波通过 90°弯管道时的传播特性作了实验研究 ,主要是气体爆轰波通过弯管道前后的火焰速度以及加速情况的研究 ,初步得出 ,爆轰波经过弯管道后单位距离上的火焰速度增量显著增加。这一研究结果证明 ,弯曲管道对于爆燃与爆轰波火焰有明显的加速作用     

无锡鼋头渚夜鹭卵中有机氯农药残留及其环境指示意义

分析了太湖鼋头渚夜鹭卵中的有机氯农药残留情况,发现在禁用近20年后,HCH的异构体、DDT及其代谢物、异狄氏剂以及环氧七氯在夜鹭卵中都不有同程度的检出,其中β－HCH和p,p‘-DDE的残留水平和检出率均很高,p,p‘-DDE平均达到了0.906ug/g(干重）。研究发现无锡夜鹭卵中多数有机氯农药残留水平平均高于江西共青城地区的样品。无锡夜鹭卵孵化率较低。可能与DDE残留量较高有关。夜鹭卵中有机氯农药残留水平具有指示环境污染的意义。     

Iron-carbon composite microspheres prepared through a facile aerosol-based process for the simultaneous adsorption and reduction of chlorinated hydrocarbons

Iron-carbon (Fe-C) composite microspheres prepared through a facile aerosol-based process are effective remediation agents for the simultaneous adsorption and reduction of chlorinated hydrocarbons. Complete dechlorination was achieved for the class of chlorinated ethenes that include tetrachloroethylene (PCE), trichloroethylene (TCE), cis- and trans-1,2-dicloroethylene (c-DCE, t-DCE), 1,1-dichloroethylene (1,1-DCE) and, vinyl chloride (VC). The Fe-C particles potentially provides multi-functionality with requisite characteristics of adsorption, reaction, and transport for the effective in situ remediation of chlorinated hydrocarbons. The carbon support immobilizes the ferromagnetic iron nanoparticles onto its surface, thereby inhibiting aggregation. The adsorptive nature of the carbon support prevents the release of toxic intermediates such as the dichloroethylenes and vinyl chloride. The adsorption of chlorinated ethenes on the Fe-C composites is higher (>80%) than that of humic acid (<35%) and comparable to adsorption on commercial activated carbons (>90%). The aerosol-based process is an efficient method to prepare adsorptive-reactive composite particles in the optimal size range for transport through the porous media and as effective targeted delivery agents for the in situ remediation of soil and groundwater contaminants.     

Decomposition of aqueous chlorinated contaminants by UV irradiation with H2O2

In the present study, the decomposition rates of carbon tetrachloride (CCl₄) and 2,4-dichlorophenol (2,4-DCP) in water by the ultraviolet (UV) light irradiation alone and H₂O₂/UV were experimentally investigated. The detailed experimental studies have been conducted for examining treatment capacities of the two different ultraviolet light sources (low and medium pressure Hg arc) in H₂O₂/UV processes. The low or medium UV lamp alone resulted in a 60%–90% decomposition of 2,4-DCP while a slight addition of H₂O₂ resulted in a drastic enhancement of the 2,4-DCP decomposition rate. The decomposition rate of 2,4-DCP with the medium pressure UV lamp alone was about 3–6 times greater than the low pressure UV lamp alone. In the direct photolysis of aqueous CCl₄, the medium pressure UV lamp had advantage over the low pressure UV lamp because the molar extinction coefficient of CCl₄ at shorter wavelength (210–220 nm) is about 20 to 50 times higher than that at 254 nm. However, adding H₂O₂ to the medium pressure UV lamp system rendered a negative oxidation rate because H₂O₂ acted as a UV absorber being competitive with CCl₄ due to negligible reaction between CCl₄ and OH radicals. The results from the present study indicated significant influence of the photochemical properties of the target contaminants on the photochemical treatment characteristics for designing cost-effective UV-based degradation of toxic contaminants.     

Microwave-assisted acid extraction of the major metal elements in herbal extracts followed by flame atomic absorption spectrometric (FAAS) determination

The content of As, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Pb, and Zn was determined in Rosa damascena, Vitis vinifera, Crocus sativus, and Olea europaea L. herbal extracts produced in different areas in Greece. Samples were mineralized in a closed microwave system using nitric acid, and the concentration of all metals was determined by flame atomic absorption spectrometry. The herbal extracts contained As, Cd, Cr, Hg, Mn, and Pb at concentrations below their respective limits of detection, whereas Cu, Fe, Mg, and Zn were determined in varying quantities. The proposed method is precise and accurate, thus it can be used for the determination of metals in Rosa damascena, Vitis vinifera, Crocus sativus, and Olea europaea L. herbal extracts.